Air heater



July 2 8, 1931. J. BOERSTRA 1,816,466

AIR HEATER Filed Jan 13, 1927 3 Sheets-Sheet l JJ A M INVENTOR BY 4 WATTORNEY:

July 28, 1931.

J. BOERSTRA AIR HEATER Filed Jan. 15, 1927 3 Sheets-Sheet '2 INVENTORATTORN EYJ:-

July 28, 1931. J. BOERSTRA 1,316,466

AIR HEATER Filed Jan. 15. 1927 s sheets-sheet a 33 Fig-'7 1 MINVENTOR wTToRNEYs Patented July 28, 1931 UNITED STATES A PATIENT OFFICE JACOBUSBOERSTRA, OF HAARLEM, NETHERLANDS, AS SIGNOR TO THE IB'ABCOCK 8c WILCOXCOMPANY, OF BAYONNE, NEW JERSEY, A CORPORATION OF.NEW JERSEY AIR HEATER.

Application filed January 13, 1927, Serial No. 160,816, and in GreatBritain May 10,1926.

This invention relates to an air heater that is especially adapted to beheated by hot waste gases from a boiler furnace, and will be understoodfrom the description in con- 5 nection with the accompanying drawings,in which Fig. 1 is a vertical section through an illustrative embodimentof the device; Fig. 2 is a vertical section on an enlarged scale showingone of the details; Fig. 3 is a section along the line 3-3 of Fig. 1;Fig. 4 is a vertical section similar to Fig. 1 showing a modification;Fig. 5 is a vertical section on an enlarged scale showing details of themodification; Fig. 6 is a section along the lines 6-6 15 of Fig. 5; Fig.7 is a vertical section through another modification and Fig. 8 is asection along the line 88 of Fig. 7.

In the drawings, reference character 1 indicates inclined tubes of awater tube boiler, over which hot gases from the boiler furnace pass,indicated by the arrow. The hot waste gases after passing from the tubes1 pass into the air heater through inner tubes 2 that are expanded intotube plates 3 and 4. The tubes 2 are surrounded by and are axial withlarger tubes 5, so that spaces are left between the inner and outertubes. The tubes 2 and are preferably made circular in cross section,but may be made of other shapes.

tubes'to rest upon the tube plate 7 with the ends of the tubes extendingthrough holes in this plate. The upper or inlet ends of the the expandedor enlarged portions 8 of adjacent tubes contacting with each other. The

tubes 2 extend beyond the tubes 5 at both ends.

A chamber at the upper ends of the tubes 2 is made up of the tube plate4 and the walls 9 from which chamber a conduit 10 leads to 4 a stack, orthe like. A chamber is also provided below the lower ends of the tubes5,

' beingmade up of the tube plates3 and 7 and the edge plates 11, fromwhich chamber a conduit 12 leads to the furnace. Air enters so thespaces between the upper'ends of the The outer tubes 5 are provided neartheir lower ends with beads 6 that enable the tubes 5 and the outsidesurfaces of the tubes 2and passes downwardly along the annular spacesbetween the tubes into the lower compartment, and thence through theconduit 12 'to the furnace while hot gases enter the lower ends of thetubes 2and pass from the upper compartment through the conduit 10 tothestack.

In the modification shown 1n Flgs. 4, 5 and 6 hot gases are passedaround the outside of the outer tubes, as well as through the innerubes, so that the air is heated on both the inner and outer surfaces ofthe annular streams of air. In this modification, the outer tubes 5' areshown as expanded into an upper tube plate 15, which structure may be,of course,'used with the otherembodinient shown in Fig.1, and the tubes5 shownin Fig. may be installed as shown in the modification, Fig. 4. Inthe modification shown in Fig. 4, the gas passage above the last pass ofthe tubes 1 is enlarged so as'to provide a space 17 along the side ofthe air heater. A damper 18 is provided to close or'open the passage tothe space. When the damper 18 is open a portion of the hot gases passinto the space 17 and thenacross the outside of thetubes 5, beingdirected across the tubes,

as shown by arrows in Fig. 6, and around the bafiie 19, and thence theypass upwardly through the outlet 10 to the stack after havi'ngjoined thehot gases that pass through the inner tubes 2. Thus the air entering theprovided from this gas passage or conduit 16', so that the hot gases'maypass either through the inner tubes or, around theouter tubes orboth. A. damper 21 is provided. for

controlling the passage of the gases to the inner tubes and a damper 22is provided for controlling the passages of the gases around theoutertubes, and a damper 23 is provided so that the gases may bebypassed instead of passing through the air heater. 'An outlet damper24is provided'for the gases passing around-the tubes and an outlet damper25 through the gas passage 16. Openings are v is provided for gasespassing through the inner tubes.

In the modification shown in Figs. 7 and 8, the inner tubes 26 areexpanded into the tube plate 27 at their exit ends and are enlarged attheir entrance ends, as. shown at 28, into conical shape and areexpanded into the plate 29. The outer tubes 30 extend between tubeplates 31 and 32 and the enlarged ends 28 of 19 the inner tubes 26 aremade ofsufiicient size to permit the outer tubes 30- to be insertedthrough the tube plate 29. Air enters through the inlet 33 between thetube plates 27 and 32 and passes through the annular 15 spaces betweenthe tubes into-the chamber between the tube plates 29 and 31-, thenceout through the exit 34 to the furnace, while hot gases pass eitherthrough the inner tubes or around the outer tubes or both, thence fromthe exit, conduit 35 tothe stack. The entire arrangement is disposed ina, chamber adjacent the conduit, as plainly shown, access to thischamber from the flue being had by means of the dampers 21, 22, 24 and2,5,. and air being; admitted, and discharged at 33 and 34 respectively.

I claim:

1. In an air heater, coaxial tubes, means for directing hot gasesthrough one set of 39 said tubes, and means for directing air throughthe other set, the inner tubes extending beyond the outer tubes and endsthereof being enlarged to at least the outer dimensions of the outertubes.

35 2. In an air heater, coaxial inner and outer tubes and means wherebyhot gases may be passed through the inner tubes, or around the outertubes, or through the inner tubes and around the outer tubes, at will.

49 3. In an air heater, a set of parallel tubes, a second set oftubes'disposed within those of the first set, an air inlet and outletcon nected respectively to the opposite ends of the tubes in the firstset, a hot gas inlet and outlet connected respectively to opposite endsofthe tubes in the second set, connections from said gas inlet andoutlet respectively to the spaces between. the'tubes in. said first set,and valves controlling the flow; through each 50 of said connections.

4. In an air heater, a set ofparallel tubes,

:1 second set of tubes disposed within those of the first set,v an airinlet and, outlet connccted respectively to the opposite ends of thetubes in the first set, a hot gas inlet and outlet connectedrespectively to opposite ends of the tubes in the secondset, connectionsfrom said gas inlet and outlet respectively'to'the spaces between thetubes in said first set, valves controlling the flow through each ofsaid connections, a by-pass connecting said hot gas inlet directly tosaid hot gas outlet, and a valve controlling said by-pass.

JACOBUS BOERSTRA.

